php oop数据库查询

Question

我正在自学php并尝试oop，我在以下问题中苦苦挣扎，有人能帮助我如何在以下数据库连接中使用另一个类函数。 在php.net中，它定义为$ mysqli = new mysqli（'localhost'，'my_user'，'my_password'，'my_db'）; 但是当我在课堂上使用它时，它是行不通的。 谢谢

class dbconnect{
private $host;
private $user;
private $pass;
private $dabase;

function doConnect()
{
    $this->host = 'localhost';
    $this->user = 'root';
    $this->pass = 'abc@123';
    $this->dabase = 'database_5';

    $db = new mysqli($this->host, $this->user, $this->pass, $this->dabase);

    if (mysqli_connect_errno())
    {
        echo "<br /><hr />";
        echo "<p style='align:center;'>Error : could not connect to database.. </p>";
        echo "<hr />";
        exit;
    } 
}   
$mysql = new dbconnect();
function doQuery($mysql){
     $queryUser = $mysql->query("SELECT * FROM b_admin_user WHERE username_d = 'admin'");
     echo $queryUser_row = $queryUser->num_rows;
} 
doQuery($mysql);

Answer 1

尝试这个

   <?php
   class MySQL {

   //objekto kintamieji
   private $host;  
   private $username;
   private $password;
   private $database;
   private $conn;  // connection

   public function __construct($set_host, $set_username, $set_password){
    $this->host = $set_host;
    $this->username = $set_username;
    $this->password = $set_password;
    // jungiuosi prie db
    $this->conn = mysql_connect($this->host, $this->username, $this->password)
                  or die("Couldn't connect");
   }

   public function database($set_database)
   {   
    $this->database=$set_database;
    //pasirenku lentele
    mysql_select_db($this->database, $this->conn) or die("cannot select Database");
   }

   }
   // jungiames
   $connect = new MySQL('localhost','root','');
   $connect->database('job');

   ?>